From e4da3edeec0384b0bae93a9721fa85e0b42a66c3 Mon Sep 17 00:00:00 2001
From: Ryan Culpepper <ryanc@racket-lang.org>
Date: Sun, 16 Dec 2012 18:52:24 -0500
Subject: [PATCH] fix popcount bug in bit-vector

---
 collects/data/bit-vector.rkt                   |  2 +-
 collects/data/private/count-bits-in-fixnum.rkt |  4 ++--
 collects/tests/data/bit-vector.rkt             | 14 +++++++++-----
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/collects/data/bit-vector.rkt b/collects/data/bit-vector.rkt
index fc6812095e..a0cd7c8226 100644
--- a/collects/data/bit-vector.rkt
+++ b/collects/data/bit-vector.rkt
@@ -21,7 +21,7 @@
 
 (define (make-bit-vector size [fill #f])
   (define-values (q r) (quotient/remainder size bits-in-a-word))
-  (define word-size (add1 q))
+  (define word-size (+ q (if (zero? r) 0 1)))
   (define words (make-fxvector word-size (if fill largest-fixnum 0)))  
   (when (and fill (not (zero? r))) 
     (fxvector-set! words q (- (expt 2 r) 1)))
diff --git a/collects/data/private/count-bits-in-fixnum.rkt b/collects/data/private/count-bits-in-fixnum.rkt
index d2b804996a..cec194422a 100644
--- a/collects/data/private/count-bits-in-fixnum.rkt
+++ b/collects/data/private/count-bits-in-fixnum.rkt
@@ -1,6 +1,6 @@
-#lang racket
+#lang racket/base
 (require racket/unsafe/ops
-         (for-syntax racket/fixnum racket/vector))
+         (for-syntax racket/base racket/fixnum racket/vector))
 (provide fxpopcount)
 ;; Count set bits for 30 bit number in 5 steps.
 ;; for 62 bit number in 6.
diff --git a/collects/tests/data/bit-vector.rkt b/collects/tests/data/bit-vector.rkt
index 4a8528c6f4..cd70a85a8c 100644
--- a/collects/tests/data/bit-vector.rkt
+++ b/collects/tests/data/bit-vector.rkt
@@ -100,13 +100,17 @@
 
 (test-case "bit-vector-popcount"
            (let ()
-             (define (test)
+             (define (test len)
                (define fill (odd? (random 2)))
-               (define bv (make-bit-vector 1000 fill))
-               (define ns (list->set (build-list 100 (λ (_) (random 1000)))))
+               (define bv (make-bit-vector len fill))
+               (define ns (list->set (build-list 100 (λ (_) (random len)))))
                (for ([n (in-set ns)]) (bit-vector-set! bv n (not fill)))
                (define count 
-                 (if fill (- 1000 (set-count ns)) (set-count ns)))
+                 (if fill (- len (set-count ns)) (set-count ns)))
                (check-equal? (bit-vector-popcount bv) count))
              (for ([i (in-range 100)])
-               (test))))
+               (test 1000))
+             ;; test multiples of possible word sizes
+             (for ([ws (in-list '(8 30 62))])
+               (for ([i (in-range 10)])
+                 (test (* ws 10))))))